Regioselective/electro-oxidative intermolecular [3 + 2] annulation for the preparation of indolines.
ABSTRACT: Compared with the reported intramolecular electro-oxidative cyclization of alkenyl amines or vinyl anilines for the preparation of pyrrolidines or indolines, the intermolecular version is less studied. Herein, this electrochemical intermolecular oxidative annulation of anilines and alkenes for the preparation of indolines proceeded under external oxidant-free conditions. The most noteworthy achievement of our work is the facile generation of indolines with quaternary centers at the 2-position. In addition, alkenes and anilines bearing various functional groups can be well tolerated. Remarkably, electrolyte-free conditions were used in an electrochemical flow cell, which shows the application potential of this method.
Project description:Chiral vicinal diamines, including 2-aminomethyl indolines and pyrrolidines, are useful as ligands for catalytic asymmetric reactions and are also found as important components of bioactive compounds. Herein is reported the first copper-catalyzed alkene diamination that occurs with high enantioselectivity. The substrate range is the broadest yet reported for this kind of intra-/intermolecular reaction sequence both with respect to ?-alkenyl sulfonamide substrate and external amine nucleophile. The resulting products expand the availability of substituted 2-aminomethyl indolines and pyrrolidines, privileged compounds in asymmetric catalysis and medicinal chemistry. A unique solution to a challenging oxidation problem related to copper catalyst turnover is also presented.
Project description:For the first time, an aza-Heck cyclization that allows the preparation of indoline scaffolds is described. Using N-hydroxy anilines as electrophiles, which can be easily accessed from the corresponding nitroarenes, this method provides indolines bearing pendant functionality and complex ring topologies. Synthesis of challenging indolines, such as those bearing fully substituted carbon atoms at C2, is also possible using this method.
Project description:Reductive cyclization of epoxides tethered to substituted anilines and aminopyridines in the presence of 3 mol % of titanocene dichloride and stoichiometric manganese metal promotes a radical annulation to form 3,3-disubstituted indolines and azaindolines.
Project description:An efficient diastereoselective rhodium catalyzed synthesis of indolines possessing two contiguous tetrasubstituted carbon centers has been achieved with good to excellent yields using <i>ortho</i>-vinylanilines and iminocarbenes derived from <i>N</i>-sulfonyl-1,2,3-triazoles. The reaction affords excellent <i>cis</i>-diastereoselectivity through the initial formation of a <i>N</i>-ylide followed by intramolecular trapping with unactivated alkenes <i>via</i> an ene-type reaction with a well-organized transition state, namely intramolecular carbenylative amination of alkenes. The developed transformation was further extended to the successful synthesis of tricyclic compounds, imidazoindolines, through reduction and hypervalent iodine mediated oxidative cyclization.
Project description:We herein describe a palladium-catalyzed formal aromaticity transfer coupling reaction between phenols and pyrrolidines or indolines to generate the corresponding <i>N</i>-cyclohexyl pyrroles or indoles. In this transformation, the aromaticity of phenols is formally passed on to the pyrrolidine or indoline units. Substituted phenols thus can serve as latent cyclohexyl equivalents for the fast construction of various <i>N</i>-cyclohexyl pyrroles and indoles.
Project description:Pin the amine on the gamma: A new method has been developed for the ?-addition of nitrogen nucleophiles to ?-substituted alkynoates or allenoates through intra- and intermolecular processes that are catalyzed by spirophosphine 1. An asymmetric version of this reaction affords enantioenriched pyrrolidines, indolines, and ?-amino-?,?-unsaturated carbonyl compounds.
Project description:A diastereo- and enantioselective CuH-catalyzed method for the preparation of highly functionalized indolines is reported. The mild reaction conditions and high degree of functional group compatibility as demonstrated with substrates bearing heterocycles, olefins, and substituted aromatic groups, renders this technique highly valuable for the synthesis of a variety of cis-2,3-disubstituted indolines in high yield and enantioeselectivity.
Project description:We have developed a formal [4+1] approach to pyrrolidines from readily available unactivated terminal alkenes as 4-carbon partners. The reaction provides a rapid construction of various pyrrolidine containing structures, especially for the diastereoselective synthesis of spiro-pyrrolidines. Mechanistic investigation suggests a Rh(III)-catalyzed intermolecular aziridination of the alkene and subsequent acid-promoted ring expansion for the pyrrolidine formation.
Project description:Intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes is realized using visible light photoredox catalysis, yielding a variety of cyclic allylic amines in fair to good yields. This method exhibits significant group tolerance particularly with heterocycles. It can also be used to prepare complex heterocycles such as fused indolines.
Project description:A bis(triflyl)ethylation [triflyl = (trifluoromethyl)sulfonyl] inserted into a sequential cyclization cascade resulted in the direct formation of <i>gem</i>-bis(triflyl)ated cyclopenta[<i>b</i>]indolines from anilide-derived allenols and alkenols. This catalyst- and irradiation-free sequence facilitated the efficient preparation of functionalized tricyclic indoline cores bearing two contiguous stereocenters. The formed cyclopenta[<i>b</i>]indolines can be easily transformed into a wide variety of triflylated indolines, including the tetracycle ring system found in polyveoline.